Subterranean hydrocarbon formations are routinely stimulated to enhance their geological permeability. A well known technique for stimulating a hydrocarbon formation is to fracture the formation by pumping into the well highly pressurized fluids containing suspended proppants, such as sand, resin-coated sand, sintered bauxite or other such abrasive particles. A fracturing fluid containing proppants is also known as a “slurry.”
As is well known in the art, a fracturing head (or “frac head”) has ports to which high pressure conduits known as “frac lines” are connected. The frac lines conduct the highly pressurized slurry from high pressure pumps to the fracturing head. The fracturing head is typically secured to a wellhead valve. The fracturing head includes a main body with a central bore for conveying the slurry downwardly into the well. Due to the high fluid pressures, high transfer rates and the abrasive properties of the proppants in the slurry, components of the fracturing head that are exposed to the pressurized slurry erode or “wash”, as such erosion is referred to by those familiar with well fracturing processes.
As is well known in the art, fracturing heads are expensive to manufacture because they are made from hardened tool steel (AISI 4140, for example). Attempts have therefore been made to provide hardened, wear-resistant inserts that can be replaced in order to extend the service life of a fracturing head. For example, published Canadian Patent Application No. 2,430,784 to McLeod et al., describes a fracturing head with a replaceable abrasion-resistant wear sleeve secured in the main bore in the body of the fracturing head. The fracturing head defines a generally Y-shaped flow path. At least two streams of fracturing slurry are pumped through respective side ports angled at approximately 45 degrees to the main bore. The two streams of slurry mix turbulently at a confluence of the side ports. The slurry then flows downstream through the main bore and into the well. The wear sleeve is positioned so that the respective streams of slurry are directed at the wear sleeve rather than at the body of the fracturing head which, being of a softer steel that that of the wear sleeve, is more prone to erosion. However, due to the location of the wear sleeve, the turbulent slurry impinges a top edge of the wear sleeve, which tapers to a feathered edge. The feathered edge of the wear sleeve thus has a tendency to erode. As the feathered top edge erodes, pressurized slurry flows between the wear sleeve and the body of the fracturing head, eroding the body of the fracturing head, causing damage.
Consequently, there exists a need for a fracturing head with improved wear resistance.